Printers are conventionally made up of a paper advancing platen to advance the paper or other recording material from a supply roll in front of a print head, a print head drive shaft to cause the print head to traverse the recording medium, and a ribbon spool with separate drive to reversibly advance the print ribbon between the print head and recording medium for the purpose of impressing a record of various calculations performed by the printer onto the recording medium.
Typically, separate drive sources have been employed to control the movement of the print ribbon, print head and paper-advancing platen. While such drive mechanisms are closely coordinated in order to synchronize advancement of the recording medium, travel of the print head and advancement of the print ribbon, the size and cost of such printers has been such as to preclude their marketing in direct competition with the small hand-held, lower cost calculators now on the market; yet there exists a real demand for calculator printers of the type which will provide a permanent or printed record of the mathematical operation of the printer in a size and at a cost competitive with the hand-held calculators. A most important factor in devising a small printer of the type described is to reduce the number and size of drive means required for controlling mechanical movement in the printer, as well as to reduce the horsepower requirements; and at the same time to establish close control over the various mechanical operations to be performed in advancing the paper, the print head and the print ribbon. In addition, the mechanical elements as described should be of the smallest possible size and arranged in the least space so as to meet the requirements of portability and size so desirable in a desk-top or hand-held printer. It is therefore proposed to provide a unique serial impact printer of the type adaptable for use as a calculator, adding machine and the like which employs a common drive mechanism having extremely low power requirements for advancing the recording medium, print head and print ribbon in closely correlated relation to one another within a minimum of space and specifically in such a way as to permit mounting of all elements on a common support which is packaged within a compact housing.